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How does the pathway to and from the basal ganglia work?
The brain sens info to the basal ganglia which goes to the thalamus and back to the brain before going down descending pathways.
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What are the four main functions of the basal ganglia?
- compares proprioceptive information and movement commands
- regulates muscle force and tone
- sequences movements
- provides semi-automatic and synergistic movement (facial expression, walking, etc)
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What are disorders of the basal ganglia called (in general)?
movement disorders
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What does the feedback loop between the cerebral cortex, the basal ganglia, and the thalamus do?
helps refine movemnts
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What forms the lentiform nucleus?
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What do the caudate nucleus, putamen, and globus pallidus form?
Corpus striatum
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What are the 6 structures of the basal ganglia?
- caudate nucleus
- putamen
- globus pallidus
- amygdala (temporal lobe-tail of caudate)
- subthalamic nucleus (in diencephalon, under thalamus)
- substantia nigra (midrain- Parkinsons)
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What forms the anterior limb of the internal capsule?
between the caudate nucleus and lentiform nucleus (putamen and globus pallidus)
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What forms the posterior limb of the internal capsule?
between the lentiform nucleus (putamen and globus pallidus) and thalamus
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What is the genu capsule?
where the anterior and posterior limbs of the internal capsule come together
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What type of fibers make up the internal capsule
corticospinal and corticobulbar
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What do the small feedback loops of the basal ganglia serve as?
- balance of facilitory and inhibitory impulses
- they are a balancing act NOT on/off switch
- if something increases that will cause something else to decrease and vice versa
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What are some hypokinetic movement disorders?
- parkinson's disease
- parkinsonism
- multiple system atrophy (MSA)
- cereballar
- ANS dysfunction
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What occurs in a hypokinetic movement disorder?
the output nuclei is increased so inhibition on the thalamus is increased so decreased facilitation of the cerebral cortex occurs
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What happens when you inhibit an inhibitory pathway?
if you inhibit an inhibitory pathway you will consequently increase a facilitory pathway
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What tracts run out of the pedunculopontine nuclei?
- reticulospinal tract
- vestibulospinal tract
- (they then travel to the LMN)
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What is the Pedunculopontine Nuclei?
- junction of cerebral peduncle and pons
- stimulation of it caues rhythmica lower limb movements needed for walking and running
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What happens if the inhibitory input of the globus pallidus internus is increased?
- the facilitory input is increased to the thalamus which consequently will decrease the facilitory pathway
- (this may not be right, I think i'm confusing myself)
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What happens when dopamine binds with D1 pathways from the substantia nigra (compacta)?
facitilitates activity in the direct pathway
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What happens when dopamine binds with D2 pathways from the substantia nigra (compacta)?
inhibits activity in the indirect pathway
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What are the 3 major facilitory inputs of the basal ganglia feedback loop?
- cerebral cortex --> caudate nucleus/putamen
- subthalamic nucleus --> globus pallidus internus substantia nigra (reticular)
- ventrolateral thalamus --> cerebral cortex
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Does GABA influence inhibitory or facilitory impulses?
inhibitory
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What NT influences facilitory pathways?
glutamate
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What are some symptoms of Parkinsons disease and what do you treat them with?
- shuffling gait, resting tremor, mask-like face
- treat with L-dopa... have to increase dosage with progression of disease
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What has occured with Parkinson's Disease?
- diminished dopamine from substantia nigra (compacta) which decreases voluntary movement
- diminished Ach in pedunculopontine nuclei which increases VST/RST activity
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What has degenerated in multiple system atrophy (MSA)?
progressive degeneration of basal ganglia, cerebellum, ANS, and cerebral cortex
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What are some symptoms of ANS dsyfunction?
- postural hypotension
- bowel and bladder incontinence
- abnormal respiration
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What occurs with cerebellar movement disorders?
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What are some hyperkinetic movement disorders?
- Huntington's Disease
- Dystonia
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What occurs in a hyperkinetic movement disorder
output of nuclei is decreased so inhibition on thalamus is decreased so facilitation of cerebral cortex is increased
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What happens with Huntington's Disease?
decreased globus pallidus internus output (drives the thalamus and stimulates the cc) causing chorea (abrupt, jerky movements) and dementia
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What happens in dystonia?
- involuntary abnormal postural twitching and repetitive movements
- non-progressive
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What are the functions of the cerebellum?
- postural balance
- ongoing movement
- movement execution
- initiation/planning
- compares anticipated movement with actual movement
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Where does all output from the cerebellum pass through?
the deep nuclei
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What is the primary input to the cerebellar cortex?
- inferior and middle cerebellar peduncles
- EXCEPT vestibulospinal and rostralspinal tract that go through superior peduncle
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What are the three lobes of the cerebellum?
- anterior lobe
- posterior lobe
- floculonodular lobe
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What does "fat guys eat donuts" stand for?
- fastigual nucleus (medial)
- globus nucleus (lateral to fastigual)
- emboliform nucleus (lateral to globus)
- dentate nucleus (most later and wraps around)
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What nuclei make up the interposed nuclei?
- globus nuclei
- emboliform nuclei
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Cells of the vermal region project where?
fastigial nucleus
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Cells of the paravermal region project where?
interposed nuclei
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Cells of the lateral region project where?
dentate nuclei
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After input has travelled into the cerebellum thru the cerebral peduncles and travel out to the cerebellar cortex then the cells do what?
project to their specific nuclei (fastigial, interposed, dentate...) which then send axons out of cerebellum through the cerebellar peduncles
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Name the region, the deep nuclei, principal output and destination, and function of the Vestibulocerebellum:
- region: floculonodular lobe
- deep nuclei: lateral vestibular
- prinicipal input: vestibular labrynth
- principal destination: medial systems- axial motor neurons
- function: axial control, postural reflex, keep you upright
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Name the region, the deep nuclei, principal output and destination, and function of the Spinocerebellum (vermal):
- region: vermis
- deep nuclei: fastigial
- principal input: proximal part of body
- principal destination: medial systems: vestibular nucleus, reticular formation (of med & lat reticulospinal tract that makes you feel nauseaus), & motor cortex
- function: axial and proximal motor control, ongoing execution of movement
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Name the region, the deep nuclei, principal output and destination, and function of the Spinocerebellum (paravermal):
- region: paravermal
- deep nuclei: interposed nuclei
- principal input: distal body parts (spinal afferents)
- principal destination: lateral systems- red nuclei, and distal regions of motor cortex
- function: distal motor control, ongoing execution (if pick up something too heavy, will modify force)
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Name the region, the deep nuclei, principal output and destination, and function of the Gerebrocerebellum:
- region: lateral hemisphere
- deep nuclei: dentate
- principal input: cortical afferents
- principal termination: integration areas- red nuclei and premotor cortex
- function: initiation, planning, timing (can do a three step process with something)
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Which output has two different parts?
spinocerebellar: vermal and paravermal
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Does the vestibulocerebllar output act through the medial activiating system or the lateral activating system?
medial activating system to control postural movements
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Does the Spinocerebellar output act through the MAS or LAS?
- both
- vermal influenced by MAS
- paravermal region influenced by LAS
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Does the Cerebrocerebellar Output act through the LAS or MAS?
lateral activating system
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What happens with a lesion to the cerebellum?
problems in the ipsilateral limbs
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What happen with a lesion in the lateral hemisphere?
limb asynergia (limb is not coordinated)
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What occurs when there is a lesion to the vermis?
trunk disorders or gait ataxia
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What happens with a lesion in the deep cerebellar nuclei and superior cerebellar peduncle?
cause more severe systems than a lesion just in the cortex
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What are some issues associated with vestibulocerebellum dysfunction?
- equilibrium off
- trunk ataxia (not smooth movements)
- wide base of support to help with balance
- nystagmus (eyes deviate slowly in 1 direction then come back)
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What are some issues associated with spinocerebellum dysfunction?
- dysartria (slurred speech, but dealing with the motor aspeect of speech)
- leg involvement/impaired gait
- gait has wide base/ataxic and can not be improved with a cane, walker, etc.
- drunken gait
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What are some issues associated with cerebrocerebellum dysfunction?
- asynergia of ipsilateral limbs
- abnormal finger to nose test
- abnormal heel to shin test
- dysmetria (can't judge distances)
- dysdiadochokinesia (rapid alternating movements)
- lack of check (can't stop movement)
- hypotonia (decrease muscle tone)
- hyporeflexes or pendular reflexes
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What are the two different routes for information going from the basal ganglia output to the LMN?
- motor thalamus --> motor areas of cerebral cortex --> corticospinal and corticobulbar neurons --> LMN
- pedunculopontine nucleus --> reticulospinal and vestibulospinal tracts --> LMN
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What is the main function of the cerebellum?
comparing actual to intended motor activity
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